Your guests will do a double take when they see this stray appendage.

Put your finger on a newfangled pen. A playful product called Model Magic ($3.25 for four ounces; dickblick.com) makes it surprisingly easy to disguise any ballpoint pen.

Pinch off a piece of Model Magic that's slightly smaller than a golf ball. Working on a clean surface, use your hands to roll and flatten the claylike material into a strip approximately 1"W x 5"L. Wrap it around a ballpoint pen, leaving the nib exposed. Roll the wrapped pen on your work surface to smooth, then use your hands and a toothpick to shape knuckles and wrinkles. Finish by inserting a fake black fingernail ($2.99 for five; partycity.com) into the clay over the nib, ensuring that the nib extends far enough to allow for writing. Let dry for one day before using.